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\multicolumn{2}{|c|}{\LARGE\bf
THE\hspace*{1cm}STAR\hspace*{1cm}FORMATION\hspace*{1cm}NEWSLETTER} \\ [0.3cm]
\multicolumn{2}{|c|}{\large\em An electronic publication dedicated to
early stellar evolution and molecular clouds} \\ [0.3cm]
{\hspace*{0.8cm} No. 16 --- 9 Dec 1993 } &
\multicolumn{1}{r|}{Editor: Bo Reipurth
(reipurth@eso.org)\hspace*{0.8cm}} \\ [-0.1cm]
& \\ \hline
\end{tabular}
\vspace*{0.5cm}
\begin{center}
{\Large\em From the Editor}
\end{center}
\vspace*{0.3cm}
The Star Formation Newsletter has now existed for a bit longer than a
year. During that time the number of subscribers, distributed all over
the world, has climbed to almost 500, including a number of libraries,
and it continues to steadily increase. From this and from the many
positive and encouraging e-mails I have received I gather that the
original goal of the Newsletter, namely to act as a rapid courier of
scientific news within the star formation community, has been largely
fulfilled. Consequently I have decided to continue with the
publication of the Newsletter beyond this trial period.
The Star Formation Newsletter is the product of a common effort of all
of its readers. By sending in the abstracts of your newly accepted
papers your results become rapidly known throughout the community,
just as you get to know about everybody elses latest works. It is my
hope that the Newsletter can reach a 90\% completeness in its coverage
of the new literature. I estimate that at present at most two thirds
of abstracts of papers on low mass star formation and molecular clouds
appear in the Newsletter. You can help to increase this percentage in
two ways: by sending your abstracts and by encouraging your colleagues
working in the field to receive and contribute to the Newsletter.
Other features of the Newsletter include the abstracts of recent Ph.D.
theses, information on meetings, new jobs, new books, and short notes
where you can make announcements or inquiries to the community.
From now on all issues of the Newsletter are available through
anonymous ftp thanks to Fionn Murtagh of ESO, who every month makes a
WAIS index of each new issue. Using WAIS you can search through all
abstracts for subjects of your interest and retrieve the corresponding
issue, if you do not already have it. See the last page for instructions.
\vspace*{0.5cm}
\begin{center}
{\Large\em Abstracts of recently accepted papers}
\end{center}
\vspace*{0.3cm}
%% Here you put between the brackets the title of your paper:
{\large\bf{ A Radio Candidate for the Exciting Source of the L1287 Bipolar
Outflow }}
%% Here comes the author(s) of the paper, you should indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Guillem Anglada$^{1,2}$, Luis F. Rodr\'\i guez$^{3,4}$ Jos\'e M.
Girart$^1$, Robert Estalella$^{1,2}$, and Jos\'e M. Torrelles$^5$ }}
%% Here, you write your institute name and the addresses, the number in $^..$
%% indicates your author number, for example:
$^1$ {Departament d'Astronomia i Meteorologia, Universitat de Barcelona,
Av. Diagonal 647, E-08028 Barcelona, Spain} \\
$^2$ {Also Laboratori d'Astrof\'\i sica, Societat Catalana de F\'\i sica,
IEC, Spain} \\
$^3$ {National Radio Astronomy Observatory, P. O. Box 0, Socorro, NM 87801,
USA} \\
$^4$ {On sabbatical leave from Instituto de Astronom\'\i a, UNAM} \\
$^5$ {Instituto de Astrof\'\i sica de Andaluc\'\i a, CSIC, Apdo. Correos 3004,
C/ Sancho Panza s/n, E-18080 Granada, Spain}
%% Within the following brackets you place your text:
{The FU Orionis phenomenon has been proposed to account for the bipolar
molecular outflows commonly observed in star forming regions. Perhaps the
best case in support of this hypothesis is the L1287 outflow, recently
suggested to be excited by a visible binary FU Ori system (RNO 1B/1C).
However, a different object has also been proposed to excite the powerful
bipolar molecular outflow in L1287: a yet undetected deeply embedded source,
inferred from polarimetric studies of the region and displaced several arc sec
from the FU Orionis system. Sensitive 3.6-cm Very Large Array observations of
the region reveal the presence of a radio continuum source coincident within
$1''$ with the predicted position of the embedded source and with the catalog
position of IRAS~00338+6312. This radio continuum source has positive
spectral index and presents evidence of elongation approximately along the
axis of the bipolar outflow. These two properties are characteristic of other
thermal radio jets known to be associated with the exciting source of bipolar
outflows. We propose that this radio continuum source is the most plausible
candidate to excite the L1287 outflow and that the relation of the visible FU
Orionis system with the outflow is unclear.}
% Here you write which journal accepted your paper, for example:
{ Accepted by The Astrophysical Journal (Letters) }
\newpage
%% Between these brackets you write the title of your paper:
{\large\bf{Momentum Transfer By Astrophysical Jets}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{Lawrence Chernin$^1$, Colin Masson$^1$, Elizabeth Gouveia Dal Pino$^2$\
and Willy Benz$^3$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Center for Astrophysics, MS 78, 60 Garden St, Cambridge MA 02138, USA} \\
$^2$ {U. de Sao Paulo, I. Astronomico e Geofisico, Sao Paulo, Brazil} \\
$^3$ {U. of Arizona, Steward Obs and Lunar and Planetary Lab, Tuscon, AZ, USA}
%% Within the following brackets you place your text:
We have used three dimensional
smoothed particle hydrodynamical simulations to
study the basic physical properties of the outflow
that is created by a protostellar jet in a dense molecular cloud.
The dynamics of the jet/cloud interaction is strongly affected by
the cooling in the shocked gas behind
the bow shock at the head of the jet.
We show that this cooling is very rapid, with
the cooling distance of the gas much less than the jet radius.
Thus, although ambient gas is initially driven away from the jet axis by
the high thermal pressure of the post-shock gas,
rapid cooling reduces the pressure
and the outflow
subsequently evolves in a momentum-conserving snowplow fashion.
The velocity of the ambient gas is high
in the vicinity of the jet head, but
decreases rapidly as more material is swept up.
Thus, this type of outflow produces
extremely high velocity clumps of post shock gas
which resemble the features seen in outflows.
We have investigated the transfer of momentum from
the jet to the ambient medium as a function of
the jet parameters. We show that a low Mach number ($\le~6$)
jet slows down rapidly because it entrains ambient material
along its sides. On the other hand,
the beam of a high Mach
number jet is separated from the ambient gas by a low density
cocoon of post-shock gas,
and this jet transfers
momentum to the ambient medium principally at the bow shock.
In high Mach number jets, as those from young stellar objects,
the dominant interaction is therefore at the bow shock at the head of the jet.
% Here you write which journal accepted your paper, for example:
{ Accepted by the Astrophysical Journal. }
\vspace*{0.5cm}
%% Between these brackets you write the title of your paper:
{\large\bf Proper motion measurements and high resolution imaging of the
HH\,46/47 outflow}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf Jochen Eisl\"offel$^{1,2}$ \ and Reinhard Mundt$^1$ }
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Max-Planck-Institut f\"ur Astronomie, K\"onigstuhl 17,
D-69117 Heidelberg, Federal Republic of Germany} \\
$^2$ {Dublin Institute for Advanced Studies, School of Cosmic Physics,
5 Merrion Square, Dublin 2, Ireland}
%% Within the following brackets you place your text:
{We have carried out a detailed study of the proper motions of the knots
in the HH\,46/47 jet and counterjet, as well as of the condensations in
the associated bow shocks HH\,47C and HH\,47D. In the jet the
tangential velocities are about 200\,km\,s$^{-1}$ with marked variations of about
$\pm$100\,km\,s$^{-1}$. In the other parts of the jet system the
average tangential velocities are somewhat lower at 70 --
170\,km\,s$^{-1}$. Given reasonable assumptions about the pattern speed
at the apex of the presumed
bow shock HH\,47A, the orientation angle of the HH\,46/47 outflow with respect
to the plane of the sky is found to be 34$^{\circ}$\,$\pm$\,3$^{\circ}$.
This enables us to correct the observed radial and tangential velocities
in the jet for projection effects allowing the local flow speed of the jet
and the knot pattern speed to be derived. A typical flow speed of about
300\,km\,s$^{-1}$ is found in the jet. Along part of the jet the knots at
its northeastern edge are clearly moving at a lower velocity than knots
closer to the jet axis. The ratio $\zeta$ between the pattern speed of
the knots and the flow speed of the jet appears to show distinct phases.
The components of lower tangential
velocity and eventually also of lower pattern speed may be created by
entrainment of the ambient material into the jet along parts of the jet
channel.
We coadded images taken under excellent seeing conditions into a single
high-signal/noise image and deconvolved the latter using the
Richardson-Lucy algorithm. The deconvolved image has a seeing of
0."47 (FWHM) and contains a wealth of structural detail. The jet
clearly shows several kinks and, most important, along most of its
length consists of
two well-separated bright rims. We discuss this unusual limb-brightening
effect, which has only been seen in a limited number of jets so far.
Proper motions were also measured for the condensations in the
arc-shaped HH-objects HH\,47D and HH\,47C, which are assumed to be the bow shocks
of the jet and the counterjet, respectively. The internal pattern of
motion of these condensations is in good agreement with predictions
from simple bow shock models.}
% Here you write which journal accepted your paper, for example:
{ Accepted by Astron. Astrophys. }
\newpage
%% Between these brackets you write the title of your paper:
{\large\bf{The Collimation of Jets and Bipolar Outflows
in Young Stellar Objects: Inertial Confinement}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{Adam Frank$^1$ \& Alberto Noriega-Crespo$^{2,3}$}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Department of Astronomy, University of Minnesota,
Minneapolis, MN 55455, USA} \\
$^2$ {Department of Astronomy, FM-20, University of Washington,
Seattle, WA 98195, USA} \\
$^3$ {Maria Mitchell Observatory, Nantucket, MA 02554, USA}
%% Within the following brackets you place your text:
%{This is the abstract of your paper}
{We describe an effective mechanism for collimating the
outflow from a YSO. Our study is based on a series of numerical
simulations of the interaction of a central, isotropic wind with a
toroidal circumstellar accretion flow. A bipolar shock configuration
is quickly established as a consequence of the decrease of the
accretion flow density from equator to pole. The jet is collimated
through the inertial confinement mechanism (Icke {\it et. al.}
1992). A prolate inner shock focuses the wind toward the axis forming
the jet. At the same time the contact discontinuity at the equator
becomes unstable and is dragged by the jet into a chimney. This
chimney confines the high-velocity gas and maintains the collimation.
The kinematical pattern of the outflow is consistent with the observations.}
% Here you write which journal accepted your paper, for example:
{Accepted by Astron. \& Astrophys.}
\vspace*{0.5cm}
%% Between these brackets you write the title of your paper:
{\large\bf{Detection of the Carbon Monoxide Ion (CO$^+$) in the Interstellar
Medium and a Planetary Nebula}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ William B. Latter$^1$, Christopher K. Walker$^2$,\ and Philip R.
Maloney$^3$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {National Radio Astronomy Observatory, Campus Building 65, 949 N.
Cherry Ave., Tucson, AZ 85721, USA (wlatter@nrao.edu)} \\
$^2$ {Steward Observatory, University of Arizona, Tucson, AZ 85721,
USA (cwalker@as.arizona.edu)} \\
$^3$ {Joint Institute for Laboratory Astrophysics, University of
Colorado, Boulder, CO 80309, USA (maloney@shapley.colo- \\rado.edu)}
%% Within the following brackets you place your text:
{We report detection of the carbon monoxide ion (CO$^+$) in
the interstellar medium (M17SW) and a planetary nebula (NGC 7027).
These detections are based on observations of three millimeter and
submillimeter transitions in M17SW and one in NGC 7027. Chemical
models suggest that CO$^+$ should be most abundant where complex
molecules are least likely to be present. In our search for
CO$^+$ we therefore minimized the chance of confusion while maximizing the
probability of detection by observing regions whose chemistry is
dominated by the effects of ultraviolet radiation.
}
% Here you write which journal accepted your paper, for example:
{ Accepted by Astrophy. J. Letters }
\vspace*{0.5cm}
%% Between these brackets you write the title of your paper:
{\large\bf{A Protostellar Jet Model for the Water Masers in W49N}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Mordecai-Mark Mac Low$^1$, Moshe Elitzur$^2$, James M. Stone$^3$
\ and Arieh K\"onigl$^1$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Department of Astronomy and Astrophysics, University of
Chicago, 5640 S. Ellis Ave., Chicago, IL 60637, USA,
mordecai@jets.uchicago.edu, arieh@jets.uchicago.edu} \\
$^2$ {Department of Physics and Astronomy,
University of Kentucky at Lexington, moshe@ukcc.uky.edu} \\
$^3$ {Department of Astronomy, University of Maryland at
College Park, jstone@astro.umd.edu}
%% Within the following brackets you place your text:
{Observations by Gwinn, Moran, \& Reid of the proper motions of water masers in
W49N show that they have an elongated distribution expanding from a common
center. Features with high space velocity only occur far from the center,
while low-velocity features occur at all distances. We propose
that these observations can be interpreted in terms of a
shell of shocked molecular gas that is driven by the expanding
cocoon of a high-velocity protostellar jet. We present 3D
numerical simulations in support of this interpretation and
argue that this source provides a unique opportunity for a
detailed study of jet-driven cocoons.}
% Here you write which journal accepted your paper, for example:
{ Accepted by Astrophys. J. }
\newpage
%% Between these brackets you write the title of your paper:
{\large\bf{The Circumstellar Environment of the FU Orionis Pre-Outburst
Candidate V1331 Cygni}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ S. McMuldroch$^1$, A. I. Sargent$^2$ \ and G. A. Blake$^1$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Div. of Geological and Planetary Sciences, 170-25 Caltech,
Pasadena, CA 91125, USA} \\
$^2$ {Div. of Physics, Mathematics, and Astronomy, 105-24 Caltech,
Pasadena, CA 91125,USA}
%% Within the following brackets you place your text:
{High resolution ($\sim$4$''$) aperture synthesis maps of the CO (1$\to$0),
$^{13}$CO.~(1$\to$0), $^{13}$CO.~(2$\to$1), and associated continuum
emission from the
FU~Orionis candidate V1331~Cygni reveal a massive, 0.5$\pm$0.15~M$_\odot$,
circumstellar disk surrounded by a flattened gaseous envelope,
6000~$\times$~4400~AU in size,
mass $\geq$0.32~M$_\odot$. These images and lower resolution measurements also
trace a bipolar outflow and gaseous ring, 4.1 by 2.8 $\times$ 10$^4$~AU, mass
$\geq$0.07~M$_\odot$, radially expanding at 22$\pm$4~km/s. We suggest this ring is
a swept-up gaseous torus from an energetic mass ejection stage, possibly an
FU~Orionis outburst or outbursts, $\sim$4~$\times$~10$^3$ years ago that imparted
$\geq$10$^{45}$~ergs into the ambient cloud.}
%This is the abstract of your paper}
% Here you write which journal accepted your paper, for example:
{ Accepted by The Astronomical Journal }
\vspace*{0.5cm}
%% Between these brackets you write the title of your paper:
{\large\bf{Statistical Analysis of Turbulence in Molecular Clouds}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Mark S. Miesch$^1$ \ and John Bally$^1$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Center for Astrophysics and Space Astronomy,
Department of Astrophysical, Planetary, and Atmospheric Sciences
University of Colorado -- Campus Box 389
Boulder, CO 80309, USA \\
miesch@janos.colorado.edu
~~bally@janos.colorado.edu}
%% Within the following brackets you place your text:
{ We present an investigation of the statistical properties of fluctuating
gas motions in five nearby molecular clouds using the two-point
autocorrelation and structure functions and the power spectra of their
radial velocity structure as traced by emission-line centroid velocities. Our
analysis includes observations made with the AT\&T Bell Laboratories
7-meter Crawford Hill antenna (1.1$^{\prime}$ beamwidth)
of $^{13}$CO $J=1\rightarrow0$ emission in
OrionB, MonR2, L1228, and L1551 and also $^{13}$CO $J=2\rightarrow1$
observations
of the molecular gas surrounding the Herbig-Haro object HH83 lying
just west of L1641 in the OrionA cloud which were obtained with a
higher spatial resolution (0.22$^{\prime}$)
using the IRAM-30m telescope on Pico Veleta,
Spain (Bally et al. 1994).
The effects of beam smoothing and the interpolation of a set of
observations onto a regular spatial grid are studied using model spectral line
data cubes and we find that the behavior of the statistical functions
presented here and those presented
elsewhere by other authors are heavily influenced by
these effects at scales comparable to and somewhat larger than the
beamwidth. At larger lags real correlations are detected and
we use the
e-folding length of the autocorrelation function (i.e. the
correlation length) to investigate the characteristic scales
of the underlying turbulent flow.
We find that this measure is dependent on the range of scales
sampled by the observations themselves both for
our data and for previously existing observations
presented by other authors and we interpret this result and the observed
similarity between the functional forms of the statistical functions
derived for different data sets
as evidence for a self-similar turbulent hierarchy of gas motions
extending over a wide range of scales in the interstellar medium.
Power law fits to the observed structure functions yield a
mean index describing the hierarchy
of $0.86\pm0.3$, which translates into a velocity dispersion
- region size relationship of the type first introduced by Larson (1981),
$\Delta V \propto l^\gamma$, with $\gamma=0.43\pm0.15$. This result is
consistent with that found by Larson in his original analysis,
$\gamma \approx 0.38$, and with the range found in more recent studies,
$0.35 < \gamma < 0.7$ (e.g. Myers 1987).
We also discuss the observed scaling
laws in relation to the predictions of phenomenological theories of
forced, isotropic turbulence. The mean turbulent stress and maximum
energy transport rate as a function of scale are obtained from the
velocity power spectra following the procedure of Kleiner \& Dickman
(1987), and the results are discussed in the context of scale-dependent
star formation and the generation of turbulence in molecular clouds.
}
% Here you write which journal accepted your paper, for example:
{ Accepted by The Astrophysical Journal}
\newpage
%% Between these brackets you write the title of your paper:
{\large\bf{ Radio Continuum, Ammonia and Water Maser Observations of
Bright, Unassociated IRAS Point Sources}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Mari Paz Miralles$^1$, Luis~F.~Rodr\'\i guez$^2$ and
Eugenio Scalise$^3$}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Instituto de Astronom\'\i a, UNAM,
Apdo. Postal 70-264,
M\'exico, DF, 04510, MEXICO.
Also Universidad Complutense de Madrid, Spain.
~~~miralles@astroscu.unam.mx \\
}
$^2$ {National Radio Astronomy Observatory,
P. O. Box 0,
Socorro, NM 87801, USA.
On sabbatical leave
from Instituto de Astronom\'\i a, UNAM.
~~~lrodrigu@aoc.nrao.edu \\
}
$^3$ {Instituto de Pesquisas Espaciaes
C.~P. 515, 12201 Sao Jose dos Campos, SP, Brazil
}
%% Within the following brackets you place your text:
{
We present matching-beam 6 and 2-cm radio continuum
observations made with the Very Large Array, and ammonia and
water maser observations made at the Haystack Observatory of 12
IRAS point sources selected from the survey of Scalise et al. (1989) of
bright, unassociated IRAS point sources. These sources have 60 or
100 $\mu$m flux densities in excess of $10^3$ Jy and
have no previous reference in any of the 37 catalogs considered for
association of IRAS sources with known sources.
Six of the twelve sources have associated radio continuum, ammonia and
water maser emission and all of them show at least one of these three emissions.
In all sources detected, the ammonia is warm (T$ \sim 20$ K) and suggests
the association of dense molecular gas with embedded heating sources. It
is argued that all sources in the sample could be associated with
time-variable H$_2$O maser emission.
The radio and far-infrared data appear to indicate that these
sources are star-forming regions, powered by a late O or
early B-type star.
Several of the sources of lower luminosity ($\sim 5 \times 10^3~L_\odot$)
appear
to have ionizing photon fluxes {\sl in excess} of those expected for a
ZAMS star. Possible explanations for this discrepancy are discussed.
}
% Here you write which journal accepted your paper, for example:
{To appear in The Astrophysical Journal (Supplements) }
\vspace*{0.5cm}
%% Between these brackets you write the title of your paper:
{\large\bf{Fabry-Perot Observations and New Models of the HH~47A and
HH~47D Bow Shocks}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Jon A. Morse$^{1,5}$, Pat Hartigan$^2$, Steve Heathcote$^3$,
John Raymond$^4$, \& Gerald Cecil$^5$}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Space Telescope Science Institute,
3700 San Martin Dr., Baltimore, MD 21218, USA} \\
$^2$ {Five College Astronomy Department, Graduate Research, Tower B, 517G,
University of Massachusetts, Amherst, MA 01003, USA} \\
$^3$ {Cerro Tololo Inter-American Observatory, National Optical Astronomy
Observatories, Casilla 603, La Serena, Chile} \\
$^4$ {Harvard-Smithsonian Center for Astrophysics, 60 Garden St.
Cambridge, MA 02138, USA} \\
$^5$ {Department of Physics and Astronomy, University of North Carolina,
CB\#3255, Phillips Hall, Chapel Hill, NC 27599-3255, USA }
%% Within the following brackets you place your text:
{
We present new models for the HH~47A and HH~47D bow shocks based on
line flux and velocity maps obtained with an imaging Fabry-Perot spectrometer.
We confirm that HH~47A and HH~47D each show a bow shock/Mach disk
morphology, and that velocity variability in the outflow
can account for the observed structures.
While it was suggested a decade ago that the inner working surface HH~47A
appears to be traveling into the wake of HH~47D,
we find kinematic evidence that the outer bow shock HH~47D is also
not the primary ejection event in the outflow but follows
in the wake of previously ejected material.
By comparing the observed line ratios and line profiles to those predicted by
our bow shock models, we find that
both bow shocks have substantially lower shock velocities than their
space motions would imply, and that the emission from each bow shock
is systematically blueshifted from the rest-frame velocity
of the ambient emission, indicating a co-moving preshock medium.
We derive kinematic ages of $\sim 1150$ yr for HH~47D and
$\sim 550$ yr for HH~47A, which implies that the stellar driving
source may undergo repetitive eruptions similar to
FU Ori-type outbursts every several hundred years.
This timescale is similar to estimates made by Reipurth and collaborators
for the separation between major outbursts in the HH~34 and HH~111
stellar jets.
}
% Here you write which journal accepted your paper, for example:
{ Accepted by Astrophys. J. }
\newpage
%% Between these brackets you write the title of your paper:
{\large\bf{W134: A New Pre-Main Sequence Double-Lined Spectroscopic Binary}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Deborah L. Padgett$^1$ and Karl R. Stapelfeldt$^2$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {2939 N. Marengo Ave. Altadena CA 91001, USA} \\
$^2$ {WFPC2 Science Team, Mail Stop 179-225 Jet Propulsion Laboratory,
4800 Oak Grove Dr., Pasadena CA 91109 USA}
%% Within the following brackets you place your text:
{
We report the discovery that the pre-main sequence star Walker 134 in
the young cluster NGC 2264 is a double-lined spectroscopic binary.
Both components are G stars with strong Li I 6708 {\AA} absorption lines.
Twenty radial velocity measurements have been used to determine the
orbital elements of this system. The orbit has a period of 6.3532 $\pm$
0.0012 days and is circular within the limits of our velocity resolution;
$e< 0.01$. The total system mass is Msin$^3i$ = 3.16 M$_{\odot}$
with a mass ratio of 1.04.
Estimates for the orbit inclination angle and stellar radii place the
system near the threshold for eclipse observability; however, no decrease
in brightness was seen during two attempts at photometric monitoring.
The circular orbit of W134 fills an important gap in the period distribution
of pre-main sequence binaries and thereby constrains the effectiveness of
tidal orbital circularization during the pre-main sequence.
}
% Here you write which journal accepted your paper, for example:
{ Accepted by Astronomical Journal }
\vspace*{0.5cm}
%% Between these brackets you write the title of your paper:
{\large\bf{A Catalog of Bright-Rimmed Clouds with IRAS Point Sources:
Candidates for Star Formation by Radiation-Driven Implosion. II.
the Southern Hemisphere}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{Koji Sugitani$^1$ \ and Katsuo Ogura$^2$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {College of General Education, Nagoya City University, Mizuho-ku,
Nagoya 467, Japan} \\
$^2$ {Kokugakuin University, Higashi, Shibuya-ku, Tokyo 150, Japan
}
%% Within the following brackets you place your text:
{Forty-five bright-rimmed clouds associated with IRAS
point sources have been selected in the southern hemisphere
from the ESO (R) Atlas in addition to the 44 objects of
the northern work (Paper I; Sugitani et al. 1991, ApJS 77, 59).
Again they are good candidates for the sites of star formation
induced by radiation-driven implosion. Four of them are known
to be associated with HH objects, and three with molecular outflows.
Most of their sizes are less than 1 pc, and the luminosities of
the associated IRAS sources, 20 to 3x$10^{4}$$L_{\odot}$,
are much larger than those of the IRAS sources associated with
Bok globules or dense cores in dark cloud complexes,
both having a similar mass range. This suggests that
intermediate mass stars or multiple star systems are mainly formed
in the bright-rimmed clouds. IRAS luminosity to cloud mass ratios
are significantly greater than those in Bok globules or dense cores.
The results confirm most of the findings of Paper I.}
% Here you write which journal accepted your paper, for example:
{ Accepted by Astronphys. J. Suppl. }
\vspace*{0.5cm}
{\large\bf{CS Multitransitional Study of Density Distribution
in Star Forming Regions II: The S140 Region }}
{\bf{Shudong Zhou$^{1,2}$, Harold M. Butner$^3$, Neal J. Evans II$^2$
Rolf G\"usten$^4$, Marc L. Kutner$^5$, and Lee G. Mundy$^6$}}
$^1${(Current address)
Department of Astronomy, University of Illinois, Urbana, IL 61801, USA}\\
$^2${Department of Astronomy, University of Texas, Austin, TX 78712, USA}\\
$^3${Carnegie Institute of Washington, Department of Terrestrial Magnetism,
5241 Broad Branch Rd. NW, Washington, DC 20015-1305, USA} \\
$^4${Max-Planck-Institute f\"ur Radioastronomie, Auf dem H\"ugel 69,
D-5300 Bonn 1, Germany}\\
$^5${Physics Department, Rensselaer Polytechnic Institute, Troy, NY
12180, USA}\\
$^6${Department of and Astronomy, University of Maryland, College Park,
MD 20742, USA}
{The S140 molecular cloud was observed
in 5 transitions of CS with resolutions of
11$''$--45$''$. The data were analyzed with both the
LVG and microturbulent models of radiative
transfer to derive the density structure.
It was found that the CS emission comes
from three components of gas: a spherical component
centered on the infrared cluster, an arc
component along the ionization front between
the S140 HII region and the dense molecular cloud core,
and a high-velocity component from the dense part of a molecular outflow.
The spherical component contributes most to
the CS emission and was analyzed in more detail
than the other components. Using a temperature distribution
derived from an analysis of
the dust emission from S140, we fit a power-law density
distribution of $n(r) = n_i(r/r_i)^{-\alpha}$ to the spherical component.
The best fit was for $n_i$ = 1.4$\times$10$^6$ (density at $r_i$ = 0.026 pc)
and $\alpha$ = 0.8.
The density ($n_i$) was found to be greater than or equal to
the density required to account for the dust emission, depending on
the dust opacity laws adopted.
The presence of optical emission (Dinerstein et al. 1979) suggests
a clumpy structure for the dense gas.
Considerations of the virial mass and the lowest amount of column
density required to produce dust emission put the volume filling
factor ($f_v$) of the dense gas at $\sim$0.14--0.5.
We compared S140 with other regions of star formation where the density
structure has been derived from excitation analysis.
Source-to-source variations in density gradients and clumpiness
clearly exist, ranging from $\alpha$ = 2 and $f_v \sim 1$ in B335
to $\alpha \sim 0$, $f_v \sim 0.1$ in M17.
There is a tendency for more massive star forming regions to have
a flatter density distribution, a more clumpy structure,
and a larger number of young stars. The implications of this
tendency are discussed.}
{ Accepted by Astrophys. J. }
\vspace*{10cm}
\fboxrule0.02cm
\fboxsep0.4cm
\fbox{\rule[-0.9cm]{0.0cm}{1.8cm}{\parbox{13cm}
{This issue and all past issues of the Star Formation Newsletter are
available, each as an individual file in LaTeX format, by anonymous ftp
from ecf.hq.eso.org (134.171.11.4) in directory /pub/star-formation. The
contents of all issues are additionally free-text searchable using WAIS, a
publicly available information retrieval package. A file in the above
anonymous ftp directory, called WAIS-FAQ.txt, provides further details on
WAIS. The procedure to follow is also described in a 'readme' file.}}}
\newpage
\begin{center}
{\Large\em Dissertation Abstracts}
\vspace*{1cm}
%% Between these brackets you write the title of your thesis:
{\Large\bf{Near-Infrared spectroscopy of shocked molecular hydrogen in star
formation regions}}
\vspace*{0.5cm}
%% Here comes your name
{\bf{ Amadeu J. L. Fernandes} }
%% Here you write the institute where your thesis work was conducted, e.g.:
{Thesis work conducted at: Dept. of Astronomy, University of Edinburgh,
Blackford Hill, Edinburgh EH9 3HJ}
%% Here comes your present postal address (if you are about to move and know
%% your coming address give it as well) e.g.:
{Current address: Centro de
Astrof\'{i}sica, Rua do Campo Alegre, 823, 4100 Porto, Portugal}
%% Here comes your e-mail address:
{Electronic mail: almfern@ciup1.ncc.up.pt}
%% Name of your adviser:
{Ph.D dissertation directed by: Peter W.J.L Brand}
%% Month and Year of thesis:
{Ph.D degree awarded: November 1993}
\vspace*{0.8cm}
\end{center}
%% Within the following brackets you place your text:
{ The work presented in
this thesis is devoted to the study of the physics of shock waves in dense
molecular cloud environments that are typical of star forming regions. The
structure of these shock waves are analysed in terms of the two basic models:
J-shock and C-shock.
We have investigated the H$_2$ emission properties from Herbig-Haro 7 and the
DR 21 bipolar outflow by measuring several spectral lines arising in the K
band. These H$_2$ lines cover a wide range in energy of the upper level
(6000-25000 K) and enables a detailed study of the temperature distribution
of the gas. The calculated column density ratios have been compared to J and
C-shock models for different shock geometries. We have shown that current
oblique J- and C-shock models fail to explain the observed H$_2$ column
density ratios. J-shock models fail to provide sufficient hot gas from behind
the shock front and are not able to explain the large line intensities
observed in the high-vibrational H$_2$ lines. The line emission from the 6
positions observed within the HH 7 bow are shown to be consistent with a
paraboloidal bow shock geometry, which however necessitates of an extra
source of excitation of the high energy levels to explain the H$_2$ line
ratios. We present a study of the effects of the UV radiation field
associated with the bow shock structure and show that a shock-induced Far-UV
radiation field with a strength of G$_0 = 10^2 - 10^3$, can account for the
observed H$_2$ line ratios. We suggest that shocks are responsible for the
low-lying level excitation of the H$_2$ molecule while Ly$\alpha$ resonance
pumping is responsible for the high-excitation line emission.
Measurements of several infrared emission lines of H$_2$ in the K window
from the DR 21 bipolar outflow, show different excitation conditions for the
East and West lobes of H$_2$ emission. The higher H$_2$ line ratios measured
for the East lobe is indicative of enhanced excitation for the
high-excitation levels of the H$_2$ molecule, which can be caused by either
shock-produced Ly$\alpha$ resonance pumping or by direct UV excitation of
H$_2$ from the central H{\sc II} region and producing higher fluorescent fluxes.
We show that the H$_2$ emission can be explained in terms of a model
consisting of a C-shock and a PDR. The H$_2$ line ratios are best fitted with
a PDR model with parameters: FUV field in the range $10^2 \leq$ G$_0 \leq
10^3$ and densities $n \geq 3 \times 10^3$ cm$^{-3}$.
We show that the H$_2$ fluorescent emission from both HH 7 and DR 21 is
reproduced better with an ortho-to-para ratio of 1.8. }
\newpage
\end{document}